Solid state detector packaging technique

ABSTRACT

A radiation detector package includes a radiation-sensitive solid-state element ( 10 ) having a first electrode ( 12 ) and a pixelated second electrode ( 14 ) disposed on opposite principal surfaces of the solid-state element. An electronics board ( 20 ) receives an electrical signal from the solid-state element responsive to radiation incident upon the radiation-sensitive solid-state element. A light-tight shield ( 40, 40 ′) shields at least the radiation-sensitive solid-state element from light exposure and compresses an insulating elastomer and metal element connector ( 30, 32 ) between the pixilated electrode ( 14 ) and contact pads ( 24 ) on the electronics board.

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of U.S. provisional application Ser.No. 60/601,253 filed Aug. 13, 2004, which is incorporated herein byreference.

The following relates to the radiation detector arts. It findsparticular application in conjunction with radiation detectors formedical imagers employing radiation transmission orradiopharmaceuticals, such as single photon emission computed tomography(SPECT) imagers, positron emission tomography (PET) imagers,transmission computed tomography (CT) imagers, and the like, and will bedescribed with particular reference thereto. However, it findsapplication in radiation detection generally, and in methods and systemsemploying radiation detectors, such as radioastronomy, airport luggagescreening, planar x-ray imaging in general, and so forth.

In single-photon emission computed tomography (SPECT), aradiopharmaceutical is administered to an imaging subject, and one ormore radiation detectors, commonly called gamma cameras, are used todetect the radiopharmaceutical via radiation emission caused byradioactive decay events. Typically, each gamma camera includes aradiation detector array and a honeycomb collimator disposed in front ofthe radiation detector array. The honeycomb collimator defines a linearor small-angle conical line of sight so that the detected radiationcomprises projection data. If the gamma cameras are moved over a rangeof angular views, for example over a 180° or 360° angular range, thenthe resulting projection data can be reconstructed using filteredbackprojection or another imaging technique into an image of theradiopharmaceutical distribution in the imaging subject. Advantageously,the radiopharmaceutical can be designed to concentrate in selectedtissues, such as the kidneys, to provide preferential imaging of thoseselected tissues.

In positron emission tomography (PET), a radiopharmaceutical isadministered to the imaging subject, in which the radioactive decayevents of the radiopharmaceutical produce positrons. Each positroninteracts with an electron to produce a positron-electron annihilationevent that emits two oppositely directed gamma rays. Using coincidencedetection circuitry, a ring array of radiation detectors surrounding theimaging subject detect the simultaneous oppositely directed gamma rayevents corresponding to the positron-electron annihilation. A line ofreaction connecting the two simultaneous detections contains theposition of the positron-electron annihilation event. Such lines ofreaction are analogous to projection data and can be reconstructed toproduce a two- or three-dimensional image.

In a planar x-ray imaging, a radiation source irradiates an imagingsubject, and a radiation detector array disposed on the opposite side ofthe imaging subject detects the transmitted radiation. Due toattenuation of radiation by tissues in the imaging subject, the detectedradiation provides a two-dimensional planar representation of bones orother hard, radiation-absorbing structures in the imaging subject. Suchtransmission-based imaging is improved upon in transmission computedtomography imaging, in which the x-ray tube or other radiation source isrevolved around the imaging subject to provide transmission views orprojection data over an extended angular range, for example over a 180°or 360° span of angular views. Using filtered backprojection or anotherimage reconstruction technique, this radiation projection data isreconstructed into a two- or three-dimensional image representation.

All of these techniques and other radiation-based medical imagingtechniques share a common need for compact and robust radiation detectorpackages. Such radiation detector packages are also used in other areas,such as in radioastronomy and airport luggage scanning. In the past,SPECT and PET radiation detector packages have typically includedphotomultiplier tubes optically coupled with scintillator crystals.Absorption of a radiation particle by the scintillator crystal producesa scintillation of light which is measured by the photomultiplier tubes.Such scintillator/photomultiplier tube radiation detectors are complex,expensive to manufacture, and fragile.

In another approach, an electrically biased solid-state radiationdetector is employed. A radiation-sensitive solid-state film or block ofmaterial, such as cadmium zinc telluride (CZT), is biased by an anodeand a cathode disposed on opposite sides of the film or block to producean electric field in the material. Absorption of a radiation particle bythe solid state material creates a plasma of electrons and holes, whichthe electric field separates. The holes go to the cathode while theelectrons go the anode, thus producing an electric detector current.Typically, either the anode or the cathode is pixelated to enable thelocation of the radiation absorption event on the face of the radiationdetector to be spatially resolved. A printed circuit board having anarray of electrical pads corresponding to the pixels of the pixelatedelectrode is secured to the radiation-sensitive solid-state materialwith the electrode pixels and the electrical pads aligned and in contactwith one another. Electronic components disposed below the electricalpads receive and process the detector signals.

Existing solid state radiation detector packages have certaindisadvantages. They typically include a direct physical connectionbetween the radiation-sensitive solid-state material and the printedcircuit board. This arrangement is susceptible to reliability problemsdue to mechanical stresses or shocks, or due to thermal stressesproduced by differential thermal expansion of the solid-state materialand the printed circuit board. Moreover, existing solid state radiationdetector packages are typically problematic from a thermal heat sinkingstandpoint, because the solid-state material is substantially thermallyisolated, and because some designs include multiple layers ofelectronics which increases the thermal resistance of heat removalpaths. In addition to producing undesirable heat retention, therelatively thermally isolated nature of the radiation-sensitivesolid-state material in typical existing solid state radiation detectorpackages makes it difficult to uniformly cool the solid-state materialto produce a uniform dark current across the radiation detector area.

The following contemplates improved apparatuses and methods thatovercome the aforementioned limitations and others.

According to one aspect, a radiation detector package is disclosed,including a radiation-sensing solid-state element. A first electrode isdisposed on a first principal surface of the solid-state element. Apixelated second electrode is disposed on a second principal surface ofthe solid-state element opposite the first principal surface. Anelectronics board receives an electrical signal from the solid-stateelement responsive to radiation incident upon the radiation-sensitivesolid-state element. A light-tight shield is provided that shields atleast the radiation-sensitive solid-state element from light exposureand compressively maintains the radiation-receiving element and theelectronics board in a preselected, electrically interconnectedrelationship.

According to another aspect, a method of making a radiation detectorpackage is disclosed. A radiation-sensing solid-state element with afirst electrode on a first principal surface and a second, pixilatedelectrode on a second, opposite principal surface, an electronics boardwith an array of electrical contact pads facing the pixilated electrode,and an electrically conductive membrane are staked with the electricallyconductive membrane between the pixilated electrode and the electricalcontract pads. The electrically conductive membrane is compressed intoelectrical and mechanical contact with the pixilated electrode and theelectrical contact pads with a light-tight shield that shields theradiation-receiving element from light.

One advantage resides in simplified radiation detector packaging withless stringent tolerances for alignment of components.

Another advantage resides in improved robustness against mechanicalstresses and shocks and against thermal heating and cooling stresses.

Another advantage resides in improved heat sinking of the radiationdetector.

Yet another advantage resides in improved thermal uniformity in activecooling of the radiation detector.

Still yet another advantage resides in providing tillable detectors withbackside electrical connections for constructing radiation detectorarrays of arbitrary size.

Numerous additional advantages and benefits will become apparent tothose of ordinary skill in the art upon reading the following detaileddescription.

The invention may take form in various components and arrangements ofcomponents, and in various process operations and arrangements ofprocess operations. The drawings are only for the purpose ofillustrating preferred embodiments and are not to be construed aslimiting the invention.

FIG. 1 shows a perspective view of a solid state radiation detectorpackage.

FIG. 2 shows a side view of the radiation detector package of FIG. 1with one side of the light-tight shield removed to reveal internalcomponents of the package.

FIG. 3 shows a perspective view of the radiation-sensitive solid-stateelement of the radiation detector package of FIG. 1, including thepixelated anode.

FIG. 4 shows an exploded side view of the radiation detector package ofFIG. 1 with the light-tight shield removed.

FIG. 5 shows a side sectional view of the light-tight shield includingthe sealing lip.

FIG. 6 shows a side view of a second radiation detector package with oneside of the light-tight shield removed to reveal internal components ofthe second radiation detector package.

FIG. 7 shows a transmission computed tomography scanner employing anabutting plurality of the radiation detector packages of FIG. 1 as anarced radiation detector array.

FIG. 8 shows a single photon emission computed tomography (SPECT)scanner with two heads each employing an abutting plurality of theradiation detector packages of FIG. 1 as a radiation detector array.

With reference to FIGS. 1-5, a radiation detector package 8 includesradiation-sensitive solid-state element 10 which in the illustratedembodiment is a cadmium zinc telluride (CZT) block. Otherradiation-sensitive materials such as cadmium telluride (CdTe) ormercury iodide (HgI), for example, can also be used as the solid stateelement. A cathode 12 is disposed on a radiation-receiving principalside of the radiation-sensitive solid-state element 10, and a pixelatedanode 14 is disposed on a second principal side or backside of theradiation-sensitive solid-state element 10 opposite theradiation-receiving side. In operation, a negative bias is applied tothe cathode 12 relative to the pixelated anode 14. When a radiationparticle is absorbed by the radiation-sensitive solid-state element 10,an electron-hole pair plasma is generated, and the electrons and holesare swept to the anode 14 and cathode 12, respectively, to generate adetector current indicative of the radiation particle. By pixilating theanode 14, the radiation particle absorption event can be spatiallylocalized on the face of the detector based on which anode pixel orsmall plurality of anode pixels conduct the detector current. Instead ofthe illustrated continuous cathode 12 and pixelated anode 14, acontinuous anode and pixelated cathode can be used for spatiallocalization with a suitable change in orientation and biasing of thesolid state element.

An electronics board 20 receives the detector signal. The electronicsboard includes a printed circuit board 22 including an array ofelectrical contact pads 24 disposed on a first principal side facing thesolid state element 10, and one or more integrated circuit components 26or other electronic components disposed on a second principal sideopposite the first principal side and distal from the solid stateelement 10. The one or more integrated circuit components 26 areconnected with the array of electrical pads 24 by printed circuitry ofthe printed circuit board 22. In some embodiments, the integratedcircuit components 26 include one or more application-specificintegrated circuits (ASIC's) performing detector signalpre-amplification, signal digitization, or other signal processing. Inother embodiments, the integrated circuit components 26 include one ormore microcontrollers, microprocessors, field-programmable gate arrays(FPGA's), or other programmable digital components for processingdigitized detector signals. Discrete circuit components such as discreteresistors or transistors can also be disposed on the second principalside of the printed circuit board 22.

The elements of the array of electrical pads 24 correspond with thepixels of the pixelated anode 14. To electrically connect the pixels ofthe pixelated anode 14 with the corresponding elements of the array ofelectrical pads 24 in a robust manner that is resistant to mechanicalstresses produced by heating, cooling, gantry rotation, or the like, atleast one electrically conductive elastic membrane 30, 32 or othercompressible connector is disposed between the pixelated anode 14 andthe array of electrical pads 24 of the electronics board 20.

In some embodiments the connector is an electrically conductivefiber-based compressible or elastic membrane 30 that includes aplurality of metal fibers or other electrically conductive fibersdispersed in a deformable membrane with the electrically conductivefibers oriented generally transverse to the plane of the elasticmembrane, i.e., vertical in the orientation of FIG. 4. The electricallyconductive fibers are thin enough to flex in compression, yet stiffenough to bias themselves to maintain contact with pads on the anode andcircuit board. The insulating, compressible material is thick enoughthat adjacent fibers do not connect electrically.

In other embodiments the elastic membrane is a plurality of zebraelastomeric connector strips 32 each including linearly alternatingelectrically conductive and electrically insulative portions. Such zebraelastomeric connector strips 32 are illustrated in FIG. 3. In FIG. 3,only five zebra elastomeric connector strips 32 are illustrated in orderto show the pixelated anode 14; however, there would in general beenough zebra elastomeric connector strips 32 to connect all the pixelsof the pixelated anode 14 with corresponding electrical pads of thearray of electrical pads 24.

The fiber-based electrically conductive elastic membrane 30 shouldemploy electrically conductive fibers having diameters and lateral fiberseparations which are substantially smaller than the size and spacing ofthe pixels of the pixelated anode 14, and the fibers should be generallyelectrically isolated from one another. In this manner, the fiber-basedelectrically conductive elastic membrane 30 conducts electrical currentin the direction transverse to the membrane 30, but does not conductelectrical current along the membrane 30. Hence, a detector currentgenerated in one pixel of the pixelated anode 14 is communicated to thecorresponding electrical pad of the array of electrical pads 24 withoutcross-talk due to lateral conduction of electrical current.

Similarly, the zebra elastomeric connectors 32 should be spaced apartfrom one another to prevent electrical conduction therebetween.Optionally, the zebra elastomeric connectors 32 can include insulativesidewalls to prevent electrical cross-talk between neighboring zebraelastomeric connectors 32. The pitch or period of the alternatingelectrically conductive and electrically insulative portions should bemuch smaller than the size and spacing of the pixels of the pixelatedanode 14 to avoid cross-talk between neighboring pixels of the pixelatedanode 14 along the zebra elastomeric connector 32. In some embodiments,the width of the zebra elastomeric connectors 32 is substantially lessthan the pixel size to prevent shorting across pixels. In otherembodiments, there is one zebra elastomeric connector 32 for eachcorresponding row of pixels of the pixelated anode 14, and the width ofeach zebra elastomeric connector 32 comports with the width of one rowof anode pixels.

The illustrated electrically conductive elastic membranes 30, 32 areexamples. Those skilled in the art can readily construct similarelectrically conductive elastic membranes having substantial electricalconductivity transverse to the membrane without substantial lateralelectrical conductivity along the membrane. Substantially anyelectrically conductive elastic membrane having such anisotropicelectrical conductivity characteristics can be used to connect thepixelated anode 14 and the array of electrical pads 24 in a mechanicallyand thermally robust manner. Moreover, the electrically conductiveportions are typically thermally conductive and the electricallyinsulating portions can be thermally insulating or conductive to controlheat transfer between the solid-state element 10 and the electronicsboard 20.

The use of the at least one electrically conductive elastic membrane 30,32 provides a number of advantages. The elastomer provides an elasticcushion to accommodate mechanical or thermal stresses. The electricallyconductive elastic membrane 30, 32 also reduces the tolerances requiredin aligning the pixels of the pixelated anode 14 with the electricalpads of the array of electrical pads 24.

Together with these advantageous mechanical properties, if the one ormore elastic membranes 30, 32 are thermally conductive, then they canprovide a large-area thermal connection between the radiation-sensitivesolid-state element 10 and the electronics board 20, which spans theactive area of the radiation detector. This large-area thermalconnection enhances thermal uniformity across the detector area for heatsinking or active cooling. In some embodiments, however, it iscontemplated to use a thermally insulating elastic membrane. Forexample, if the one or more integrated circuit components 26 produce alarge quantity of heat, it may be advantageous to use a thermallyinsulating elastic membrane to thermally isolate the radiation-sensitivesolid-state element 10 from the electronics board 20.

A light-tight shield 40 shields the radiation-sensitive solid-stateelement 10 from exposure to light or other electromagnetic radiationhaving substantially lower energies than the radiation intended to bedetected. Such shielding reduces dark currents in theradiation-sensitive solid-state element 10. The illustrated light-tightshield 40 includes a front principal side disposed over thelight-receiving principal side of the radiation-sensitive solid-stateelement 10 (that is, the side on which the cathode 12 is disposed) and aplurality of sidewalls extending from edges of the front principal sideacross sidewalls of the solid-state element 10 and electronics board 20.The sidewalls of the light-tight shield 40 connect with a thermallyconductive plate 44 disposed on the second principal side of theelectronics board 20 distal from the radiation-sensitive solid-stateelement 10. The thermally conductive plate 44 is disposed on thebackside of the radiation detector package 8. In the illustratedembodiment, the light-tight shield 40 includes a lip 46, 48 (labeled inFIG. 5) that mates with a slots 50, 52 of the thermally conductive plate44 (slots shown in phantom in FIG. 4). Other coupling arrangements canbe used. The light-tight shield 40 and the thermally conductive plate 44together define a housing containing the radiation-sensitive solid-stateelement 10, the electronics board 20, and the electrically conductiveelastic membrane 30, 32.

The radiation-sensitive solid-state element 10, the electronics board20, and the electrically conductive elastic membrane 30, 32 arecompressively held between the connected light-tight shield 40 and thethermally conductive plate 44. The compression facilitates thermalcontact between the thermally conductive plate 44 and the one or moreintegrated circuit components 26, and also facilitates electricalconnection between the pixelated anode 14 and the array of electricalpads 24 via the electrically conductive elastic membrane 30, 32. Aninsulating isolation sheet or membrane 56 is disposed between thecathode 12 and the light-tight shield 40 to provide electrical isolationtherebetween.

The compression provided by the light-tight shield 40 and the thermallyconductive plate 44 holds the radiation-sensitive solid-state element 10and the electronics board 20 together. To align the pixelated anode 14of the radiation-sensitive solid-state element 10 and the array ofelectrical pads 24 of the electronics board 20, a plurality of alignmentpins 64, 66 pass through alignment holes 70, 72 of the electronics board20 (shown in phantom in FIG. 4), through corresponding alignment holes74, 76 of the radiation-sensitive solid-state element 10 (shown in FIG.3 and in phantom in FIG. 4). Optionally, a heat sinking element 80 isdisposed on the backside of the radiation detector package 8 in contactwith the thermally conductive plate 44. For example, the heat sinkingelement 80 can be a Peltier board or device.

In some embodiments, the radiation detector package 8 is actively cooledby the Peltier board 80, a surrounding liquid coolant flow or immersion,or so forth. When the package 8 is cooled below the dew point such thatwater would normally condense inside of the package 8, it isadvantageous to eliminate water vapor from inside of the package 8.Toward that end, the connection between the light-tight shield 40 andthermally conductive plate 44 is optionally a hermetic seal, achievedfor example by applying an epoxy or other sealant at the connection ofthe lip 46, 48 of the shield 40 and the slots 50, 52 of the plate 44. Byfabricating the radiation detector package 8 in a dry nitrogen or otherlow moisture environment, and then hermetically sealing the housing inthe low moisture environment, water condensation within the package 8 isreduced or avoided. Alternatively, the radiation detector package 8 canbe fabricated in moisture-containing air up to and including hermeticsealing together of the shield 40 and plate 44, followed by backfillingof the housing by dry nitrogen or another inert gas through suitableopenings (not shown) in the shield 40 or plate 44 (or through a gaptherebetween intentionally left during the hermetic sealing), finallyfollowed by hermetic sealing of the backfilling openings by an epoxy orthe like.

The radiation detector package 8 has sides that are buttable with otherdetector packages to define large area radiation detector arrays. One ormore backside electrical connectors 84, 86 are disposed on the same sideof the electronics board 20 as the one or more integrated circuitcomponents 26. The backside electrical connectors 84, 86 pass throughopenings 90, 92 in the thermally conductive plate 44 (shown in phantomin FIG. 4) to provide external electrical accessibility. By placing theelectrical connectors 84, 86 on the backside of the radiation detectorpackage 8, the sides of the package 8 are unimpeded and can abut sidesof another similar radiation detector package 8. This enables aplurality of the radiation detector packages 8 to be tiled to form alarger-area radiation detector array.

With reference to FIG. 6, another radiation detector package 8′ includesthe radiation-sensitive solid-state element 10 with cathode 12 andpixelated anode 14 electrically coupled with the array of electricalpads 24 of the electronics board 20 via the electrically conductiveelastic membrane 30, 32, as in the detector package 8. However, theradiation detector package 8′ omits the thermally conductive plate 44. Alight-tight shield 40′ similar to the light-tight shield 40 of thepackage 8 couples instead with a circuit board 22′ that is similar tothe circuit board 22, optionally modified by including slots (not shown)for receiving the lip of the light-tight shield 40′. Since the thermallyconductive plate 44 is omitted, shorter backside electrical connectors84′, 86′ can be employed in the radiation detector package 8′.

The radiation detectors 8, 8′ or their equivalents can be employed insubstantially any type of application that calls for detectingradiation. For example, the radiation detectors 8, 8′ or theirequivalents can serve as radiation detectors in a transmission computedtomography imager, a single-photon computed tomography (SPECT) imager, apositron emission tomography (PET) imager, a planar x-ray system, aradiotelescope, an airport luggage scanning system, or so forth.

With reference to FIG. 7, a transmission computed tomography imagingscanner 110 includes an x-ray tube 112 and a two-dimensional radiationdetector array constructed of tiled radiation detector packages 8mounted on a rotating gantry 116 on opposite sides of an imaging region120. (The x-ray tube 112, radiation detector packages 8, and rotatinggantry 116 are exposed in FIG. 7 for expository purposes; however, itwill be appreciated that typically these components are enclosed in astationary gantry housing). An imaging subject (not shown) is disposedon a patient support 122 and moved into the imaging region 120 forcomputed tomography imaging. It will be noted that adjacent radiationdetector packages 8 in the scanner 110 are arranged tilted with respectto one another to define an arced detector having a curvature thatsubstantially comports with a fan-, wedge-, or cone-beam of x-raysproduced by the x-ray tube 112.

With reference to FIG. 8, a single photon emission computed tomography(SPECT) scanner 130 includes a plurality of gamma detector heads 132,134 arranged on robotic gantry arms 136, 138 to view an imaging region140. Each gamma camera 132, 134 includes an array of radiation detectorpackages 8. Typically, a honeycomb, parallel-hole, slat, pin hole,diverging, converging, or other type of collimator (not shown) isdisposed in front of the radiation detector packages 8 to define linearor small-angle conical lines-of-sight or other suitable views for eachpixel. An imaging subject (not shown) is disposed on a patient support142 and moved into the imaging region 140 for computed tomographyimaging. The radioactivity dose of the radiopharmaceutical is typicallylow so as not to injure the imaging subject. Accordingly, the gammacameras 132, 134 are advantageously mounted on the robotic gantry arms136, 138 rather than on a rotating gantry, and the arms 136, 138 movethe cameras 132, 134 conformally with the outer shape of the imagingsubject to minimize camera-to-subject distance and thus maximize thedetected radiation intensity.

The computed tomography scanner 110 of FIG. 7 includes the x-ray tube112 which typically generates a relatively high flux of lower energyx-rays. Accordingly, the radiation detector packages 8 in the computedtomography scanner 110 suitably employ a relatively thinradiation-sensitive solid-state element 10, for example a 2 millimeterthick CZT film or block. Due to the high levels of radiation produced bythe x-ray tube 112, it is contemplated to include a ground plane (notshown) containing a radiation-absorptive high-Z material in the printedcircuit board 22 of the radiation detector packages 8 to reduce theradiation exposure of the underlying one or more integrated circuitcomponents 26.

In contrast, the gamma cameras 132, 134 of the SPECT scanner 130 of FIG.8 typically receive a relatively lower flux of higher energy radiationdue to a relatively low concentration of radiopharmaceuticaladministered to the imaging subject. Accordingly, the radiation detectorpackages 8 in the SPECT scanner 130 typically employ a relativelythicker radiation-sensitive solid-state element 10 due to the higherenergy radiation, for example a 5-10 millimeter thick CZT film or block.More generally, the thickness of the radiation-sensitive solid-stateelement 10 is selected based on the radiation-stopping efficiency of thematerial, the energy (e.g., keV) of the particles, and similarconsiderations.

While two example medical imaging scanners 110, 130 have beenillustrated, it will be appreciated that the radiation detectors 8, 8′are readily employed in other radiation-based medical imagers, such aspositron emission tomography (PET) scanners and planar x-ray imagers.Moreover, the radiation detectors 8, 8′ are readily employed in otherapplications such as radioastronomy and airport luggage scanning.

The invention has been described with reference to the preferredembodiments. Obviously, modifications and alterations will occur toothers upon reading and understanding the preceding detaileddescription. It is intended that the invention be construed as includingall such modifications and alterations insofar as they come within thescope of the appended claims or the equivalents thereof.

1. A radiation detector package comprising: a radiation sensing solidstate element; a first electrode disposed on a first principal surfaceof the solid state element; a pixelated second electrode disposed on asecond principal surface of the solid state element opposite the firstprincipal surface; an electronics board receiving an electrical signalfrom the solid state element responsive to radiation incident upon theradiation sensitive solid state element; a light tight shield shieldingat least the radiation sensitive solid state element from light exposureand compressively maintaining the radiation-sensing element and theelectronics based in a preselected, electrically interconnectedrelationship; and at least one electrically conductive membrane disposedbetween the pixelated second electrode and the electronics board, theelectrically conductive membrane providing electrical connection betweenpixels of the pixelated second electrode and corresponding electricalpads of the electronics board; and a thermally conductive plate inthermal communication with elements of the electronics board, the lighttight shield and the thermally conductive plate being connectedtogether, the radiation sensitive solid state element, electronicsboard, and electrically conductive membrane being compressively heldbetween the connected thermally conductive plate and light tight shield.2. The radiation detector package as set forth in claim 1, wherein theconnection between the light tight shield and the thermally conductiveplate hermetically seals the radiation sensitive solid state element,electronics board, and electrically conductive elastic membrane insideof a housing defined by the light tight shield and thermally conductiveplate and further including a dry atmosphere inside the housing.
 3. Aradiation detector package comprising: a radiation sensing solid stateelement; a first electrode disposed on a first principal surface of thesolid state element; a pixelated second electrode disposed on a secondprincipal surface of the solid state element opposite the firstprincipal surface; an electronics board receiving an electrical signalfrom the solid state element responsive to radiation incident upon theradiation sensitive solid state element; a light tight shield shieldingat least the radiation sensitive solid state element from light exposureand compressively maintaining the radiation-sensing element and theelectronics based in a preselected, electrically interconnectedrelationship, the light tight shield including a front principal sidedisposed over the radiation sensitive solid state element and aplurality of sidewalls extending from edges of the front principal sideacross sidewalls of the solid state element and electronics board, thesidewalls connecting with one of (i) the electronics board and (ii) athermally conductive plate disposed on a side of the electronics boarddistal from the radiation sensitive solid state element; and at leastone electrically conductive membrane disposed between the pixelatedsecond electrode and the electronics board, the electrically conductivemembrane providing electrical connection between pixels of the pixelatedsecond electrode and corresponding electrical pads of the electronicsboard.
 4. The radiation detector package as set forth in claim 3,further including: an insulating layer disposed between the light-tightshield and the first electrode.
 5. The radiation detector package as setforth in claim 3, wherein the electronics board includes: a printedcircuit board, the electrical pads of the electronics board beingdisposed on a first principal side of the printed circuit board; and oneor more integrated circuit components disposed on a second principalside of the electronics board opposite the first principal side of theprinted circuit board, the one or more integrated circuit componentsbeing electrically connected with the electrical pads on the firstprincipal side by printed circuitry of the printed circuit board.
 6. Theradiation detector package as set forth in claim 5, further includes: athermally conductive plate abutting the integrated circuit components,the light-tight shield being deformed around the thermally conductiveplate compressively gripping the electrically conductive membranebetween the pixelated second electrode and the pads.
 7. The radiationdetector package as set forth in claim 3, wherein the radiationsensitive solid state element is a CZT crystal.
 8. A radiation detectorpackage comprising: a radiation sensing solid state element; a firstelectrode disposed on a first principal surface of the solid stateelement; a pixelated second electrode disposed on a second principalsurface of the solid state element opposite the first principal surface;an electronics board receiving an electrical signal from the solid stateelement responsive to radiation incident upon the radiation sensitivesolid state element; a light tight shield shielding at least theradiation sensitive solid state element from light exposure andcompressively maintaining the radiation-sensing element and theelectronics based in a preselected, electrically interconnectedrelationship; and at least one electrically conductive membrane disposedbetween the pixelated second electrode and the electronics board, theelectrically conductive membrane providing electrical connection betweenpixels of the pixelated second electrode and corresponding electricalpads of the electronics board; wherein the electronics board includes: aprinted circuit board, the electrical pads of the electronics boardbeing disposed on a first principal side of the printed circuit board,one or more integrated circuit components disposed on a second principalside of the electronics board opposite the first principal side of theprinted circuit board, the one or more integrated circuit componentsbeing electrically connected with the electrical pads on the firstprincipal side by printed circuitry of the printed circuit board, andone or more electrical connectors disposed on the second principal sideof the printed circuit board such that the radiation detector packagehas a radiation sensitive first principal package side, a secondprincipal package side opposite the first principal package side withthe one or more electrical connectors, and a plurality of packagesidewalls extending between the first and second principal sides, thesidewalls being buttable with sidewalls of other radiation detectorpackages to enable tiling of a plurality of radiation detector packagesas a radiation detector array.
 9. The radiation detector package as setforth in claim 8, wherein the light tight shield and the electronicsboard are connected together, the radiation sensitive solid stateelement and the electrically conductive elastic membrane beingcompressively held between the connected light tight shield andelectronics board.
 10. A method of making a radiation detector packagecomprising: stacking (i) a radiation-sensing solid-state element with afirst electrode on a first principal surface and a second pixelatedelectrode on a second, opposite principle surface, (ii) an electronicsboard with an array of electrical contact pads facing the pixelatedelectrode, (iii) an electrically conductive membrane between thepixelated electrode and the electrical contact pads, and (iv) a coldplate on an opposite side of the electronics board from the radiationsensing element; and compressing the electrically conductive membraneinto electrical and mechanical contact with the pixelated electrode andthe electrical contact pads with a light-tight shield that shields theradiation receiving element from light, the compressing includingbending the light-tight shield around the cold plate.
 11. The methodaccording to claim 10, wherein the light-tight shield is hermeticallysealed to the cold plate and further including: before the compressingstep, filling the package with dry gas.
 12. A radiation detector packagemade according to the method of claim
 10. 13. A method of medicalimaging comprising: sensing radiation exiting a patient with thedetector package of claim 12; reconstructing a medical diagnostic imagefrom the sensed radiation.
 14. An imaging detector comprising: aradiation-sensing solid-state element; a first electrode disposed on afirst surface of the solid-state element; a pixelated second electrodedisposed on a second surface of the solid-state element; an electronicsboard receiving an electrical signal from the solid-state elementresponsive to radiation incident upon the solid state element; and atleast one electrically conductive membrane disposed between thepixelated second electrode and the electronics board, the electricallyconductive membrane providing electrical connection between the pixelsof the pixelated second electrode and selected portions of theelectronics board, the at least one electrically conductive membranecomprising at least one of: (i) an elastic membrane and (ii) anelectrically conductive membrane having anisotropic electricalconductivity transverse to the membrane without substantial lateralelectrical conductivity along the membrane.
 15. The imaging detector ofclaim 14 wherein the at least one electrically conductive membranedisposed between the pixelated second electrode and the electronicsboard is an elastic membrane.
 16. The imaging detector of claim 14wherein the at least one electrically conductive membrane disposedbetween the pixelated second electrode and the electronics board hasanisotropic electrical conductivity transverse to the membrane withoutsubstantial lateral electrical conductivity along the membrane.
 17. Animaging detector comprising: a radiation-sensing solid-state element; afirst electrode disposed on a first surface of the solid-state element;a pixelated second electrode disposed on a second surface of thesolid-state element; an electronics board receiving an electrical signalfrom the solid-state element responsive to radiation incident upon thesolid state element; and at least one electrically conductive membranedisposed between the pixelated second electrode and the electronicsboard, the electrically conductive membrane providing electricalconnection between the pixels of the pixelated second electrode andselected portions of the electronics board, the electrically conductivemembrane being compressively held between pixelated second electrode andthe electronics board.
 18. A medical imager selected from a groupconsisting of: (i) a single photon emission computed tomography (SPECT)imager, (ii) a positron emission tomography (PET) imager, and (iii) atransmission computed tomography imager, the medical imager employing animaging detector as set forth in claim
 17. 19. The imaging detector ofclaim 17 further comprising a housing shielding at least a portion ofthe solid-state element from light exposure.
 20. The imaging detector ofclaim 19 wherein the housing provides compressive force that acts uponthe electrically conductive membrane.
 21. A radiation detector packagecomprising: a radiation sensing solid state element; a first electrodedisposed on a first principal surface of the solid state element; apixelated second electrode disposed on a second principal surface of thesolid state element opposite the first principal surface; an electronicsboard receiving an electrical signal from the solid state elementresponsive to radiation incident upon the radiation sensitive solidstate element; a light tight shield shielding at least the radiationsensitive solid state element from light exposure and compressivelymaintaining the radiation-sensing element and the electronics based in apreselected, electrically interconnected relationship; and at least oneelectrically conductive membrane disposed between the pixelated secondelectrode and the electronics board, the electrically conductivemembrane providing electrical connection between pixels of the pixelatedsecond electrode and corresponding electrical pads of the electronicsboard, wherein the at least one electrically conductive membranedisposed between the pixelated second electrode and the electronicsboard is an elastic membrane having anisotropic electrical conductivitytransverse to the membrane without substantial lateral electricalconductivity along the membrane.
 22. The radiation detector package asset forth in claim 21, wherein the electrically conductive membraneincludes: an electrically insulating elastic membrane with spaced,flexible, electrically conductive elements dispersed therein, theelectrically conductive elements being oriented generally transverse tothe plane of the electrically insulating elastic membrane.
 23. Theradiation detector package as set forth in claim 22, wherein theelectrically conductive elements are fibers.